Seven balls and a balance problem - IQ quiz 1

30 May, 2011

You have eight balls all of the same size. Seven of them weigh the same, and one of them weighs slightly more. How can you find the ball that is heavier, if you are given a weight balance and only two weightings?

Type: IQ quiz
Source- Software Engineer, Job interview question @ Google








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Solution:
Take 6 of the 8 balls and put 3 on each side of the scale. 
IF the scale is balanced THEN
     Remove those balls and put remaining two balls on one each side of the scale. 

    The side where scale goes down has the more weight ball.
ELSE (The scale is not balanced)
    Pick any 2  from the side goes down (more weight side) and put them on the scale one each.
    IF the scale is balanced THEN
        you know third one is more weight.
    ELSE (The scale is not balanced)
        The side goes down has the more weight ball

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3 comments:

Anonymous said...

1. Put 4 & 4 to two sides.
Identify the 4 most weighted.

2. Put 2 & 2 to two sides.
Identify the 2 most weighted.

3. Put 1 & 1 to two sides.
Identify the most weighted.

Uditha Madumal
(I think u remember me. I was working with u in P&O)

:D

Nalaka Gamage said...

Hi Annonimous (Udith),
Yah I remember you well working @ Virtusa P & O. :-). Nice to hear at least through the blog after so long.

By the way Udith, you got the answer bit wrong it seems may be because misread the last sentence.

Your solution need three weight attempts. Expected answer (As give down the post) have only two attempts.

I did Uditha's method... facepalm when I rembembered I was only given two chances :D :D :D XD

 
 
 

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